Cable operated doors such as garage doors are well known in the art. A garage door is usually connected to an overhead counterbalancing mechanism that provides a counterbalancing force in order to decrease the force required to open the door and also facilitate its closing. The garage door is connected to the counterbalancing mechanism by means of two cables, one at the right and one at the left. The cables are usually made of steel. The lower free end of each cable is attached at the bottom of the door.
It is also known in the art that occasionally, for one reason or the other, one of the cable brakes or one of the elements holding such cables undergoes failure, leading to the garage door falling all the way down, causing damages or even personal injuries. There have been many attempts to come up with safety devices used in the event of a failure of a cable or of an element holding the same.
Known in the art is U.S. Pat. No. 5,291,686 to SEARS et al. This patent describes an overhead door safety apparatus for a cable controlled door whose movement is guided by a stationary guide track. The apparatus includes a brake assembly which is attached to the door and which is responsive to a decrease in a predetermined cable tension. When the decrease in the predetermined cable tension takes place, the overhead door safety apparatus is actuated causing the brake assembly to apply a braking action on movement of the overhead door. More specifically, in the brake assembly, a cable-tension-responsive track follower guides motion of the door by following the track. The cable-tension-responsive track follower has a first and a second operating state. The first operating state permits smooth movement of the cable-tension-responsive track follower along the track as the door moves when a control cable maintains a predetermined amount of cable tension. The second operating state of the cable-tension-responsive track follower is automatically actuated and automatically provides a braking action against the track to halt movement of the overhead door when a control cable has less than the predetermined amount of a cable tension, such as when a counterbalance spring breaks or when the cable itself breaks.
Also known in the art is U.S. Pat. No. 4,520,591 to CALVAGNO. This patent describes a safety lock assembly for use with a garage door to prevent the latter from falling uncontrollably in the event the counterweight system supporting the garage door fails. The invention has a pivoted arm biased into a position blocking door movement. The counterweight system is attached to the pivoted arm to overcome the bias. In the event of a failure in the weight supporting members, the built-in bias will move the arm into its position where further significant movement of the door is prevented.
Also known in the art is U.S. Pat. No. 3,958,367 to FAIRMAN. This patent describes a safety device for use in combination with elongated coil springs substantially balancing the door weight for ease of opening and adapted to urge the door toward an open position after partial opening movement. The safety device comes into play in the event that a coil spring breaks. The safety device includes an elongated flexible member extending longitudinally substantially axially through the elongated spring and substituting for the spring in the event that the spring breaks. The extent to which the door moves after breakage of a spring depends upon the extent of stretching that the elongated flexible safety member undergoes after the spring breaks.
Also known in the art are the following U.S. patents which describe different safety methods and safety apparatuses for garage doors and the like: U.S. Pat. Nos. 4,019,442; 4,697,676; 4,750,294; 4,813,305; 4,956,938; 5,090,522; 5,239,777; 5,353,859; 5,419,010; 5,490,662; 5,581,939; 5,615,723; 5,684,372; and 5,743,046.
None of the above-mentioned patents provides a simple, compact, reliable and cost effective safety device for stopping downward movement of a cable operated door, such as garage doors and the like, in the event of a failure of one of the cables holding such cable operated door or in the event of a failure of one of the elements holding the cables.
Therefore, there is a need for a more compact, more reliable, easier to use, easier to maintain, safer, and more cost effective safety device for stopping downward movement of a cable operated door, such as garage doors and the like, in the event of a failure of one of the cables holding such cable operated door or in the event of a failure of one of the elements holding the cables, than what is available in the prior art.